Systems and methods for vehicle fuel system and evaporative emissions system diagnostics

Abstract

Methods and systems are provided for a fuel system of a hybrid vehicle. In one example, a system may include a fuel tank selectively fluidly coupled to a fuel vapor canister via a first conduit that includes a fuel tank isolation valve and via a second conduit that includes a tank pressure control valve and a pump. In one example, the pump is a vacuum pump.

The invention claimed is: 
     
       1. A system, comprising:
 a first conduit fluidly coupling a fuel tank to a fuel vapor canister and a second conduit fluidly coupling the fuel tank to the fuel vapor canister, wherein the first conduit includes a fuel tank isolation valve and the second conduit includes a tank pressure control valve and a vacuum pump; and 
 a controller with computer-readable instructions stored thereon that when executed enable the controller to:
 close the fuel tank isolation valve; 
 activate the vacuum pump to initiate a diagnostic leak test of the fuel tank; and 
 open the tank pressure control valve to depressurize the fuel tank. 
 
 
     
     
       2. The system of  claim 1 , wherein the fuel vapor canister is fluidly coupled to a vent line that includes a canister ventilation valve. 
     
     
       3. The system of  claim 1 , wherein the fuel tank is arranged on a hybrid vehicle. 
     
     
       4. A hybrid vehicle, comprising:
 a fuel tank fluidly coupled to a fuel vapor canister via a first conduit comprising a fuel tank isolation valve and via a second conduit comprising a vacuum pump, wherein the second conduit further comprises a tank pressure control valve arranged between the fuel tank and the vacuum pump; and 
 a controller with computer-readable instructions stored on non-transitory memory thereof that when executed enable the controller to: 
 activate the vacuum pump; 
 close the fuel tank isolation valve; 
 open a canister vent valve to conduct a diagnostic test; and 
 deactivate the vacuum pump and close the canister vent valve in response to a vacuum generated between the vacuum pump and the tank pressure control valve being greater than or equal to an initial threshold, wherein the second conduit is shaped to flow vacuum through the vacuum pump that is deactivated to a vent line to equilibrate the vent line with the second conduit. 
 
     
     
       5. The hybrid vehicle of  claim 4 , wherein the canister vent valve is arranged in the vent line fluidly coupling the fuel vapor canister to an ambient atmosphere. 
     
     
       6. The hybrid vehicle of  claim 4 , wherein the diagnostic test is a first diagnostic test, wherein the instructions further enable the controller to close the tank pressure control valve to block vacuum from flowing to the fuel tank. 
     
     
       7. The hybrid vehicle of  claim 4 , wherein the diagnostic test is a second diagnostic test, wherein the instructions further enable the controller to open the tank pressure control valve to allow vacuum to flow to the fuel tank. 
     
     
       8. A fuel system for a hybrid vehicle, comprising:
 a fuel tank comprising a first conduit selectively fluidly coupling the fuel tank to a fuel vapor canister, the first conduit comprising a fuel tank isolation valve; 
 a second conduit selectively fluidly coupling the fuel tank to the fuel vapor canister, the second conduit arranged in parallel to the first conduit and configured to bypass the fuel tank isolation valve, the second conduit including a vacuum pump and a tank pressure control valve; 
 a vent line selectively fluidly coupling the fuel vapor canister to an ambient atmosphere, the vent line comprising a canister ventilation valve; and 
 a controller with computer-readable instructions stored on non-transitory memory thereof that when executed enable the controller to:
 activate the vacuum pump, close the tank pressure control valve, close the fuel tank isolation valve, and open the canister ventilation valve until an initial threshold vacuum is generated between the vacuum pump and the tank pressure control valve to conduct a diagnostic test. 
 
 
     
     
       9. The fuel system for the hybrid vehicle of  claim 8 , wherein the instructions further enable the controller to deactivate the vacuum pump and close the canister ventilation valve, wherein the vacuum pump is configured to allow vacuum from the second conduit to flow to and equilibrate with the vent line to decrease a vacuum of the second conduit and increase a vacuum of the vent line to an equilibration threshold. 
     
     
       10. The fuel system for the hybrid vehicle of  claim 8 , wherein the second conduit comprises a diameter greater than a diameter of the first conduit. 
     
     
       11. The fuel system for the hybrid vehicle of  claim 8 , wherein the vacuum pump and the tank pressure control valve are arranged adjacent to opposite extreme ends of the second conduit. 
     
     
       12. The fuel system for the hybrid vehicle of  claim 8 , wherein the instructions further enable the controller to activate the vacuum pump and open the tank pressure control valve in response to a fuel tank pressure exceeding a threshold fuel tank pressure. 
     
     
       13. The fuel system for the hybrid vehicle of  claim 8 , wherein the instructions further enable the controller to activate the vacuum pump and open the tank pressure control valve in response to a refueling request being present. 
     
     
       14. The fuel system for the hybrid vehicle of  claim 8 , wherein the canister is fluidly coupled to an intake passage of an engine via a purge line, the purge line comprising a purge valve. 
     
     
       15. The fuel system for the hybrid vehicle of  claim 8 , wherein the second conduit branches off the first conduit, and where the tank pressure control valve is arranged at a first extreme end of the second conduit between the fuel tank isolation valve and the fuel tank, wherein the vacuum pump is arranged at a second extreme end, opposite the first extreme end, of the second conduit between the fuel tank isolation valve and the canister.